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  <title>Version 1.69.0</title>
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            <div class="section-title">
              <h1>Version 1.69.0</h1>
            </div>

            <div class="section-body">
              <h2><span class=
              "news-title">Version 1.69.0</span></h2>

              <p><span class=news-date">December 12th, 2018 02:58 GMT</span></p>
              <p><a href="/doc/libs/1_69_0/">Documentation</a>
              <table class="download-table"><caption>Downloads</caption><tr><th scope="col">Platform</th><th scope="col">File</th><th scope="col">SHA256 Hash</th></tr>
<tr><th scope="row" rowspan="2">unix</th><td><a href="https://dl.bintray.com/boostorg/release/1.69.0/source/boost_1_69_0.tar.bz2">boost_1_69_0.tar.bz2</a></td><td>8f32d4617390d1c2d16f26a27ab60d97807b35440d45891fa340fc2648b04406</td></tr><tr><td><a href="https://dl.bintray.com/boostorg/release/1.69.0/source/boost_1_69_0.tar.gz">boost_1_69_0.tar.gz</a></td><td>9a2c2819310839ea373f42d69e733c339b4e9a19deab6bfec448281554aa4dbb</td></tr>
<tr><th scope="row" rowspan="2">windows</th><td><a href="https://dl.bintray.com/boostorg/release/1.69.0/source/boost_1_69_0.7z">boost_1_69_0.7z</a></td><td>af05616f71006f97833e130aad886c96136457511ace4b5496d6566e69cbe0ca</td></tr><tr><td><a href="https://dl.bintray.com/boostorg/release/1.69.0/source/boost_1_69_0.zip">boost_1_69_0.zip</a></td><td>d074bcbcc0501c4917b965fc890e303ee70d8b01ff5712bae4a6c54f2b6b4e52</td></tr></table>
              <div class="news-description">
                <div class="description">


  <div id="version_1_69_0.notes_for_non_windows_users">
    <h3><span class="link">Notes for non-Windows
    users</span></h3>
    <p>
      The Boost build system now supports visibilities. If you are building shared
      libraries, they will use hidden visibility by default. As a result Boost shared
      libraries become smaller, load faster and have less chances to get a symbol
      collision.
    </p>
    <p>
      See <a href="/build/manual/develop/index.html#bbv2.builtin.features.visibility">Boost.Build
      visibility and local-visibility</a> for more info.
    </p>
    <p>
      To disable that feature you can use use a command line <code><span class="special">./</span><span class="identifier">b2</span> <span class="identifier">visibility</span><span class="special">=</span><span class="identifier">global</span></code> to
      build.
    </p>
  </div>
  <div id="version_1_69_0.new_libraries">
    <h3><span class="link">New Libraries</span></h3>
    <ul>
      <li>
        <div>
          <span class="library"><a href="/libs/safe_numerics/">Safe Numerics</a>:</span> A library
          for guaranteed correct integer arithmetic for C++14 and later, from Robert
          Ramey.
        </div>
      </li>
    </ul>
  </div>
  <div id="version_1_69_0.updated_libraries">
    <h3><span class="link">Updated Libraries</span></h3>
    <ul>
      <li>
        <div>
          <span class="library"><a href="/libs/any/">Any</a>:</span>
          <ul>
            <li>
              <div>
                Fixed issue with visibility. Now <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">any</span></code>
                variables constructed in one shared library with hidden visibility
                could be used and destroyed in other shared library with hidden visibility.
              </div>
            </li>
            <li>
              <div>
                Maintenance: dropped some dependencies on other Boost libraries,
                fixes for docs.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/asio/">Asio</a>:</span>
          <ul>
            <li>
              <div>
                Fixed a problem with the detection of <code><span class="identifier">std</span><span class="special">::</span><span class="identifier">future</span></code>
                availability with libstdc++.
              </div>
            </li>
            <li>
              <div>
                Fixed compile error in regex overload of <code><span class="identifier">read_until</span></code>.
              </div>
            </li>
            <li>
              <div>
                Fixed a timer heap corruption issue that can occur when moving a
                cancelled timer.
              </div>
            </li>
            <li>
              <div>
                Fixed detection of <code><span class="identifier">std</span><span class="special">::</span><span class="identifier">experimental</span><span class="special">::</span><span class="identifier">string_view</span></code>
                and <code><span class="identifier">std</span><span class="special">::</span><span class="identifier">string_view</span></code> with newer clang/libc++.
              </div>
            </li>
            <li>
              <div>
                Fixed MSVC version detection for availability of <code><span class="identifier">std</span><span class="special">::</span><span class="identifier">invoke_result</span></code>.
              </div>
            </li>
            <li>
              <div>
                Fixed the buffer sequence traits to test the new requirements, if
                <code><span class="keyword">decltype</span></code> is available.
              </div>
            </li>
            <li>
              <div>
                Fixed an MSVC issue when building with exceptions disabled.
              </div>
            </li>
            <li>
              <div>
                Added SSL context options for TLS v1.3.
              </div>
            </li>
            <li>
              <div>
                Added a compile-time test for TLS v1 support.
              </div>
            </li>
            <li>
              <div>
                Fixed the macro used to test for TLS v1.2 support.
              </div>
            </li>
            <li>
              <div>
                Prevented global objects from being created once per thread on Windows.
              </div>
            </li>
            <li>
              <div>
                Fixed a crash when using <code><span class="identifier">size</span><span class="special">()</span></code>, <code><span class="identifier">max_size</span><span class="special">()</span></code> or <code><span class="identifier">empty</span><span class="special">()</span></code> on default-constructed resolver
                results.
              </div>
            </li>
            <li>
              <div>
                Changed to move the return value in <code><span class="identifier">basic_resolver_results</span><span class="special">::</span><span class="identifier">begin</span><span class="special">()</span></code> to avoid copying.
              </div>
            </li>
            <li>
              <div>
                Enabled move support for the Intel Compiler.
              </div>
            </li>
            <li>
              <div>
                Fixed <code><span class="identifier">std</span><span class="special">::</span><span class="identifier">string_view</span></code> detection issue when
                using clang-cl.
              </div>
            </li>
            <li>
              <div>
                Fixed the handler tracking operation name for <code><span class="identifier">io_context</span><span class="special">::</span><span class="identifier">executor_type</span><span class="special">::</span><span class="identifier">dispatch</span></code>.
              </div>
            </li>
            <li>
              <div>
                Fixed a buffer overflow that could occur when parsing an address
                string with a 64-bit scope id.
              </div>
            </li>
            <li>
              <div>
                Added examples showing how to write composed operations.
              </div>
            </li>
            <li>
              <div>
                Added C++11 versions of the Timeouts, Timers, SOCKS4 and SSL examples.
              </div>
            </li>
            <li>
              <div>
                Fixed minor issues in documentation and examples.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/assign/">Assign</a>:</span>
          <ul>
            <li>
              <div>
                Add rvalue reference, perfect forwarding, and variadic template support
                (<a href="https://github.com/boostorg/assign/pull/6">PR#6</a>) (<a href="https://svn.boost.org/trac/boost/ticket/10477">#10477</a>)
              </div>
            </li>
            <li>
              <div>
                Avoid conversion to container's allocator (<a href="https://github.com/boostorg/assign/pull/29">PR#29</a>) (<a href="https://svn.boost.org/trac/boost/ticket/5419">#5419</a>)
                (<a href="https://svn.boost.org/trac/boost/ticket/7364">#7364</a>)
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/beast/">Beast</a>:</span>
          <ul>
            <li>
              <div>
                This version fixes some issues in the examples, and provides a new
                experimental socket which supports built-in timeouts on asynchronous
                operations.
              </div>
            </li>
            <li>
              <div>
                New CppCon 2018 <a href="https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/examples.html#beast.examples.cppcon_2018">websocket
                chat example</a> and <a href="https://www.youtube.com/watch?v=7FQwAjELMek">presentation
                video</a>.
              </div>
            </li>
            <li>
              <div>
                For a complete list of changes, please view the official <a href="/libs/beast/doc/html/beast/release_notes.html">Release
                Notes</a>.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/circular_buffer/">CircularBuffer</a>:</span>
          <ul>
            <li>
              <div>
                Use the empty base optimization for storing allocators that are empty
                and not final (Glen Fernandes).
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/concept_check/">Concept Check</a>:</span>
          <ul>
            <li>
              <div>
                Removed dependency on mpl. (<a href="https://github.com/boostorg/concept_check/pull/14">PR#14</a>)
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/context/">Context</a>:</span>
          <ul>
            <li>
              <div>
                <a href="https://github.com/boostorg/context/issues/85">#85</a>: duplicate alias should be missing GCC alias
              </div>
            </li>
            <li>
              <div>
                <a href="https://github.com/boostorg/context/issues/87">#87</a>: the clang-win toolset (clang-cl.exe) uses masm from
                the underlying msvc
              </div>
            </li>
            <li>
              <div>
                <a href="https://github.com/boostorg/context/issues/90">#90</a>: remove useless lines in Jamfile.v2
              </div>
            </li>
            <li>
              <div>
                <a href="https://github.com/boostorg/context/issues/91">#91</a>: add .file section for *_elf_gas.S files
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/core/">Core</a>:</span>
          <ul>
            <li>
              <div>
                Implemented <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">empty_value</span></code>,
                for library authors to conveniently leverage the Empty Base Optimization
                to store objects of potentially empty types (Glen Fernandes). This
                facility is now used in Boost.Beast, Boost.CircularBuffer, Boost.MultiArray,
                and more.
              </div>
            </li>
            <li>
              <div>
                Implemented <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">quick_exit</span></code>
                to provide the C++11 standard library facility <code><span class="identifier">std</span><span class="special">::</span><span class="identifier">quick_exit</span></code>
                functionality (Peter Dimov).
              </div>
            </li>
            <li>
              <div>
                Reduced the number of statics in Lightweight Test, and employ lighter
                abort behavior for MSVC compilers upon failure to call <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span></code> (Glen Fernandes).
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/dll/">DLL</a>:</span>
          <ul>
            <li>
              <div>
                Resolved link issues with the smart library <a href="https://github.com/boostorg/dll/issues/20">#20</a>.
              </div>
            </li>
            <li>
              <div>
                Maintenance: fixes for docs and tests.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/dynamic_bitset/">Dynamic Bitset</a>:</span>
          <ul>
            <li>
              <div>
                Performance improvements (over 2x in some cases). (<a href="https://github.com/boostorg/dynamic_bitset/pull/26">PR#26</a>)
              </div>
            </li>
            <li>
              <div>
                Added range-based set, reset, flip methods (<a href="https://github.com/boostorg/dynamic_bitset/pull/27">PR#27</a>)
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/fiber/">Fiber</a>:</span>
          <ul>
            <li>
              <div>
                <a href="https://github.com/boostorg/fiber/issues/181">#181</a>: unbuffered_channel push not return
              </div>
            </li>
            <li>
              <div>
                <a href="https://github.com/boostorg/fiber/issues/182">#182</a>: Remove UTF-8 BOM at begining of the file
              </div>
            </li>
            <li>
              <div>
                <a href="https://github.com/boostorg/fiber/issues/183">#183</a>: Fix boost-install use; should only be issued once
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/filesystem/">Filesystem</a>:</span>
          <ul>
            <li>
              <div>
                Don't use <code><span class="identifier">readdir_r</span></code>
                on Linux and Android since the <code><span class="identifier">readdir</span></code>
                function is already thread-safe. (<a href="https://github.com/boostorg/filesystem/pull/68">PR#68</a>, <a href="https://github.com/boostorg/filesystem/issues/72">#72</a>)
              </div>
            </li>
            <li>
              <div>
                Fixed crashes in <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">filesystem</span><span class="special">::</span><span class="identifier">copy</span></code>
                due to undefined behavior in the implementation. (<a href="https://github.com/boostorg/filesystem/pull/71">PR#71</a>)
              </div>
            </li>
            <li>
              <div>
                Fixed undefined behavior in <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">filesystem</span><span class="special">::</span><span class="identifier">directory_iterator</span></code>
                implementation. (<a href="https://github.com/boostorg/filesystem/pull/77">PR#77</a>)
              </div>
            </li>
            <li>
              <div>
                Fixed compilation errors when using directory iterators with <code><span class="identifier">BOOST_FOREACH</span></code>.
              </div>
            </li>
            <li>
              <div>
                Removed workarounds for older PGI C++ compiler versions to fix compilation
                on the newer ones. (<a href="https://github.com/boostorg/filesystem/pull/49">PR#49</a>)
              </div>
            </li>
            <li>
              <div>
                Fixed MSVC warnings about narrowing conversions. (<a href="https://github.com/boostorg/filesystem/pull/44">PR#44</a>)
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/flyweight/index.html">Flyweight</a>:</span>
          <ul>
            <li>
              <div>
                Fixed some issues in GCC related to Boost.MPL placeholder expression
                handling.
              </div>
            </li>
            <li>
              <div>
                Maintenance fixes.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/function/">Function</a>:</span>
          <ul>
            <li>
              <div>
                Removed dependencies on mpl, test (<a href="https://github.com/boostorg/function/pull/20">PR#20</a>) (<a href="https://github.com/boostorg/function/pull/22">PR#22</a>)
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/geometry/">Geometry</a>:</span>
          <ul>
            <li>
              <div>
                Improvements
                <ul>
                  <li>
                    <div>
                      <a href="https://github.com/boostorg/geometry/pull/486">PR#486</a> Karney's solution of direct geodesic problem
                      for internal use (thanks to Adeel Ahmad).
                    </div>
                  </li>
                  <li>
                    <div>
                      <a href="https://github.com/boostorg/geometry/pull/490">PR#490</a> Discrete Frechet and Hausdorff distance algorithms
                      (thanks to Yaghyavardhan Singh Khangarot).
                    </div>
                  </li>
                  <li>
                    <div>
                      <a href="https://github.com/boostorg/geometry/pull/496">PR#496</a> New run-time and upgraded compile-time SRS
                      transformation interfaces (undocumented for now due to potential
                      interface changes).
                    </div>
                  </li>
                </ul>
              </div>
            </li>
            <li>
              <div>
                Solved issues
                <ul>
                  <li>
                    <div>
                      <a href="https://github.com/boostorg/geometry/issues/520">#520</a> Missing documentation for dsv().
                    </div>
                  </li>
                  <li>
                    <div>
                      <a href="https://github.com/boostorg/geometry/issues/521">#521</a> Wrong documentation description for distance().
                    </div>
                  </li>
                  <li>
                    <div>
                      <a href="https://github.com/boostorg/geometry/issues/524">#524</a> Fixed 'enumeration values not handled in switch'
                      warnings.
                    </div>
                  </li>
                  <li>
                    <div>
                      <a href="https://github.com/boostorg/geometry/issues/527">#527</a> Workaround for VS 2017 (msvc-15).
                    </div>
                  </li>
                </ul>
              </div>
            </li>
            <li>
              <div>
                Bugfixes
                <ul>
                  <li>
                    <div>
                      <a href="https://github.com/boostorg/geometry/pull/505">PR#505</a> Fixed overflow in overlay algorithms (thanks
                      to Dane Springmeyer).
                    </div>
                  </li>
                  <li>
                    <div>
                      <a href="https://github.com/boostorg/geometry/pull/518">PR#518</a> Fixed passing of temporaries in append() (thanks
                      to xventura81).
                    </div>
                  </li>
                  <li>
                    <div>
                      <a href="https://github.com/boostorg/geometry/pull/522">PR#522</a> Support python3 in building documentation.
                    </div>
                  </li>
                </ul>
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/integer/">Integer</a>:</span>
          <ul>
            <li>
              <div>
                <code><span class="identifier">boost</span><span class="special">/</span><span class="identifier">pending</span><span class="special">/</span><span class="identifier">integer_log2</span><span class="special">.</span><span class="identifier">hpp</span></code> header is deprecated and will
                be removed in future releases. Use <code><span class="identifier">boost</span><span class="special">/</span><span class="identifier">integer</span><span class="special">/</span><span class="identifier">integer_log2</span><span class="special">.</span><span class="identifier">hpp</span></code>
                instead.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/iostreams/">Iostreams</a>:</span>
          <ul>
            <li>
              <div>
                Remove call to nonexistent member seekpos() of std::fpos (<a href="https://github.com/boostorg/iostreams/pull/58">PR#58</a>)
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/iterator/">Iterator</a>:</span>
          <ul>
            <li>
              <div>
                Fixed compilation problems with ambiguous unqualified calls to <code><span class="identifier">advance</span></code> and <code><span class="identifier">distance</span></code>
                on iterators whose types involve types in the namespace <code><span class="identifier">boost</span></code>. (<a href="https://github.com/boostorg/iterator/issues/43">#43</a>)
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/lexical_cast/">LexicalCast</a>:</span>
          <ul>
            <li>
              <div>
                Fixed sign-conversion warnings <a href="https://svn.boost.org/trac/boost/ticket/8991">#8991</a>.
              </div>
            </li>
            <li>
              <div>
                Maintenance: dropped some dependencies on other Boost libraries,
                fixed build system warnings.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/log/">Log</a>:</span>
          <ul>
            <li>
              <div>
                General changes:
                <ul>
                  <li>
                    <div>
                      Updated syslog sink backend to avoid using deprecated Boost.ASIO
                      interfaces. (<a href="https://github.com/boostorg/log/issues/59">#59</a>)
                    </div>
                  </li>
                </ul>
              </div>
            </li>
            <li>
              <div>
                Bug fixes:
                <ul>
                  <li>
                    <div>
                      Fixed a possible incorrect estimation of the total size of
                      rotated files in the target directory of a text file sink in
                      some cases.
                    </div>
                  </li>
                </ul>
              </div>
            </li>
            <li>
              <div>
                See <a href="/libs/log/doc/html/log/changelog.html">changelog</a>
                for more details.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/logic/">Logic</a>:</span>
          <ul>
            <li>
              <div>
                <strong>Breaking change:</strong> Use explicit operator
                bool when available (<a href="https://github.com/boostorg/logic/pull/5">PR#5</a>)
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/math/">Math</a>:</span>
          <ul>
            <li>
              <div>
                Add LambertW functions.
              </div>
            </li>
            <li>
              <div>
                Update integration routines to support complex valued integrands
                and contour integrals.
              </div>
            </li>
            <li>
              <div>
                Added the derivative of the Barycentric rational approximation.
              </div>
            </li>
            <li>
              <div>
                Minor fixes to better support variable precision floating point types.
              </div>
            </li>
            <li>
              <div>
                Removed use of deprecated Boost.Endian in favour of Predef.
              </div>
            </li>
            <li>
              <div>
                Updated continued fraction and series evaluation code to support
                complex types.
              </div>
            </li>
            <li>
              <div>
                Prevent logic error leading to infinite loop in toms748_solve. See
                <a href="https://github.com/boostorg/math/issues/138">#138</a>.
              </div>
            </li>
            <li>
              <div>
                Fix mean and standard_deviation for extreme_value_distribution. See
                <a href="https://github.com/boostorg/math/issues/139">#139</a>.
              </div>
            </li>
            <li>
              <div>
                Improve heuristics used in newton_raphson_iterate. See <a href="https://github.com/boostorg/math/issues/145">#145</a>.
              </div>
            </li>
            <li>
              <div>
                Fix result of <code><span class="identifier">erf</span><span class="special">(</span><span class="identifier">NaN</span><span class="special">)</span></code>. See <a href="https://github.com/boostorg/math/issues/141 #141">#141 #141</a>.
              </div>
            </li>
            <li>
              <div>
                Big push to reduce GCC warnings. See <a href="https://github.com/boostorg/math/issues/136 #136">#136 #136</a>.
              </div>
            </li>
            <li>
              <div>
                Refactor polynomial addition. See <a href="https://github.com/boostorg/math/pull/132">PR#132</a>.
              </div>
            </li>
            <li>
              <div>
                Fix for vxWorks having a <code><span class="identifier">real</span></code>
                function in the global namespace. See <a href="https://github.com/boostorg/math/pull/131">PR#131</a>.
              </div>
            </li>
            <li>
              <div>
                Improve <code><span class="identifier">sinc</span></code> approximations
                and add better tests.
              </div>
            </li>
            <li>
              <div>
                Fix typo in Student's T hypothesis testing documentation, see <a href="https://github.com/boostorg/math/issues/143">#143</a>.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/mp11/">Mp11</a>:</span>
          <ul>
            <li>
              <div>
                Implemented the <code><span class="identifier">mp_starts_with</span></code>
                facility (Glen Fernandes).
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/multi_array/">MultiArray</a>:</span>
          <ul>
            <li>
              <div>
                Improve C++11 allocator model support including: Support for C++11
                minimal allocators, support for stateful allocators, using the allocator
                for construction and destruction of the value type, and using the
                empty base optimization for storing empty or stateless allocators
                (Glen Fernandes).
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/multi_index/">Multi-index Containers</a>:</span>
          <ul>
            <li>
              <div>
                Introduced an alternative <a href="/libs/multi_index/doc/tutorial/key_extraction.html#key">terse
                key specification syntax</a> for C++17 compliant environments.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/multiprecision/">Multiprecision</a>:</span>
          <ul>
            <li>
              <div>
                Big update to better support variable precision types so that the
                precision of the result is always the largest of all the arguments.
              </div>
            </li>
            <li>
              <div>
                Add support for allocators that are <code><span class="identifier">final</span></code>
                in __cpp_int (Glen Fernandes).
              </div>
            </li>
            <li>
              <div>
                Removed use of deprecated Boost.Endian in favour of Predef.
              </div>
            </li>
            <li>
              <div>
                Add support for <code><span class="identifier">std</span><span class="special">::</span><span class="identifier">string_view</span></code>.
              </div>
            </li>
            <li>
              <div>
                Fixed minor bug in constant initialization. See <a href="https://github.com/boostorg/multiprecision/issues/67">#67</a>.
              </div>
            </li>
            <li>
              <div>
                Make assignment of non-finite value to <code><span class="identifier">cpp_int</span></code>
                a runtime errors. See <a href="https://github.com/boostorg/multiprecision/issues/58">#58</a>.
              </div>
            </li>
            <li>
              <div>
                Added typedefs for <code><span class="identifier">cpp_bin_float_oct</span></code>
                and <code><span class="identifier">cpp_complex_oct</span></code>.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/poly_collection/">PolyCollection</a>:</span>
          <ul>
            <li>
              <div>
                Added Boost.PolyCollection-specific versions of algorithms <code><span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each_n</span></code> and <code><span class="identifier">std</span><span class="special">::</span><span class="identifier">sample</span></code>.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/pool/">Pool</a>:</span>
          <ul>
            <li>
              <div>
                Replace boost::mutex use to avoid a dependency on Boost.Thread (<a href="https://github.com/boostorg/pool/pull/23">PR#23</a>)
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/preprocessor/">Preprocessor</a>:</span>
          <ul>
            <li>
              <div>
                Supports the new C++ standard conforming preprocessor in VC++ 14.1,
                which is currently enabled by using the /experimental:preprocessor
                switch, in Visual Studio 2017 15.8 on up.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/rational/">Rational</a>:</span>
          <ul>
            <li>
              <div>
                Add constexpr support (<a href="https://github.com/boostorg/rational/pull/28">PR#28</a>) (<a href="https://github.com/boostorg/rational/pull/32">PR#32</a>)
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/spirit/">Spirit</a>:</span>
          <ul>
            <li>
              <div>
                Spirit.X3:
                <ul>
                  <li>
                    <div>
                      Drop own FP routines in favor of <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span></code>
                      (<a href="https://github.com/boostorg/spirit/issues/392">#392</a>) (<a href="https://svn.boost.org/trac/boost/ticket/13531">#13531</a>)
                    </div>
                  </li>
                  <li>
                    <div>
                      Missing visibility mark on exception types (<a href="https://github.com/boostorg/spirit/issues/409">#409</a>)
                    </div>
                  </li>
                  <li>
                    <div>
                      to_utf8: Fixed wchar_t handling on Windows (<a href="https://github.com/boostorg/spirit/issues/413">#413</a>)
                      (<a href="https://github.com/boostorg/spirit/issues/395">#395</a>)
                    </div>
                  </li>
                </ul>
              </div>
            </li>
            <li>
              <div>
                Spirit V2
                <ul>
                  <li>
                    <div>
                      Drop own FP routines in favor of <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span></code>
                      (<a href="https://github.com/boostorg/spirit/issues/392">#392</a>) (<a href="https://svn.boost.org/trac/boost/ticket/13531">#13531</a>)
                    </div>
                  </li>
                  <li>
                    <div>
                      Missing visibility mark on exception types (<a href="https://github.com/boostorg/spirit/issues/409">#409</a>)
                    </div>
                  </li>
                  <li>
                    <div>
                      Fixed transform_attribute ambiguity (<a href="https://github.com/boostorg/spirit/issues/407">#407</a>) (<a href="https://github.com/boostorg/spirit/issues/396">#396</a>)
                    </div>
                  </li>
                  <li>
                    <div>
                      to_utf8: Fixed wchar_t handling on Windows (<a href="https://github.com/boostorg/spirit/issues/413">#413</a>)
                      (<a href="https://github.com/boostorg/spirit/issues/395">#395</a>)
                    </div>
                  </li>
                </ul>
              </div>
            </li>
            <li>
              <div>
                Spirit.Classic:
                <ul>
                  <li>
                    <div>
                      Missing visibility mark on exception types (<a href="https://github.com/boostorg/spirit/issues/409">#409</a>)
                    </div>
                  </li>
                </ul>
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/stacktrace/">Stacktrace</a>:</span>
          <ul>
            <li>
              <div>
                <code><span class="identifier">libbacktrace</span></code> usage
                was significantly improved. <code><span class="identifier">BOOST_STACKTRACE_USE_BACKTRACE</span></code>
                or <code><span class="identifier">boost_stacktrace_backtrace</span></code>
                users are encouraged to update:
                <ul>
                  <li>
                    <div>
                      Memory consumprion dropped down.
                    </div>
                  </li>
                  <li>
                    <div>
                      Stack capturing became faster by an order of magnitude.
                    </div>
                  </li>
                  <li>
                    <div>
                      <code><span class="identifier">syminfo</span></code> fallback
                      enabled to provide information for visible symbols even without
                      debug information (thanks to github user driesdeschout!)<a href="https://github.com/boostorg/stacktrace/issues/60">#60</a>,
                      <a href="https://github.com/boostorg/stacktrace/issues/61">#61</a>.
                    </div>
                  </li>
                  <li>
                    <div>
                      Exact location of the <code><span class="identifier">backtrace</span><span class="special">.</span><span class="identifier">h</span></code>
                      header now can be specified via <code><span class="identifier">BOOST_STACKTRACE_BACKTRACE_INCLUDE_FILE</span></code>,
                      to allow <code><span class="identifier">backtrace</span><span class="special">.</span><span class="identifier">h</span></code>
                      header usage on platforms and compilers where that header is
                      unreachable otherwise (for example Ubuntu Xenial + Clang) <a href="https://github.com/boostorg/stacktrace/issues/59">#59</a>.
                    </div>
                  </li>
                </ul>
              </div>
            </li>
            <li>
              <div>
                Optimized stack capturing if <code><span class="identifier">max_depth</span></code>
                is set (thanks to Jan Eisenhauer for the PR!) <a href="https://github.com/boostorg/stacktrace/issues/67">#67</a>.
              </div>
            </li>
            <li>
              <div>
                Added <code><span class="identifier">to_string</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">stacktrace</span><span class="special">&amp;</span> <span class="special">)</span></code>
                functions for fast conversion of stacktraces to <code><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code>
                <a href="https://github.com/boostorg/stacktrace/issues/57">#57</a>.
              </div>
            </li>
            <li>
              <div>
                Maintenance: updated docs <a href="https://github.com/boostorg/stacktrace/issues/62">#62</a>, tests updated.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/system/">System</a>:</span>
          <ul>
            <li>
              <div>
                Boost.System is now header-only. A stub library is still built for
                compatibility, but linking to it is no longer necessary.
              </div>
            </li>
            <li>
              <div>
                Even more functions have been marked <code><span class="keyword">constexpr</span></code>.
              </div>
            </li>
            <li>
              <div>
                The destructor of <code><span class="identifier">error_category</span></code>
                is now <code><span class="keyword">protected</span></code> and
                no longer <code><span class="keyword">virtual</span></code>. This
                is a potentially breaking change, but its impact is expected to be
                limited.
              </div>
            </li>
            <li>
              <div>
                <code><span class="identifier">error_category</span></code> now
                has a constructor that accepts a 64 bit identifier, enabling distinct
                category objects to compare equal.
              </div>
            </li>
            <li>
              <div>
                The constructors of <code><span class="identifier">error_category</span></code>
                are now <code><span class="keyword">protected</span></code>.
              </div>
            </li>
            <li>
              <div>
                A non-allocating, nonthrowing overload of <code><span class="identifier">message</span></code>
                has been added.
              </div>
            </li>
            <li>
              <div>
                A virtual function <code><span class="identifier">failed</span></code>
                has been added, allowing categories for which success is not synonymous
                with 0.
              </div>
            </li>
            <li>
              <div>
                The deprecated <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">throws</span></code>
                object has been removed.
              </div>
            </li>
            <li>
              <div>
                <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">throws</span><span class="special">()</span></code>
                is now deprecated and its use is discouraged.
              </div>
            </li>
            <li>
              <div>
                The constructor of <code><span class="identifier">system_error</span></code>
                taking a single <code><span class="identifier">error_code</span></code>
                argument is now <code><span class="keyword">explicit</span></code>.
              </div>
            </li>
            <li>
              <div>
                <code><span class="identifier">system_error</span><span class="special">::</span><span class="identifier">code</span><span class="special">()</span></code>
                now returns by value.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/test/">Test</a>:</span>
          <ul>
            <li>
              <div>
                Boost.test v3.9 see the <a href="libs/test/doc/html/boost_test/change_log.html">Changes
                log</a> for more details.
              </div>
            </li>
            <li>
              <div>
                New feature:
                <ul>
                  <li>
                    <div>
                      Official support of header-only variant of Boost.Test with
                      multiple translation units.
                    </div>
                  </li>
                  <li>
                    <div>
                      Now possible to manually add a test case by specifying its
                      name, with <code><span class="identifier">BOOST_TEST_CASE_NAME</span></code>
                    </div>
                  </li>
                  <li>
                    <div>
                      Better support of <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">exception</span></code>
                      in the logs
                    </div>
                  </li>
                </ul>
              </div>
            </li>
            <li>
              <div>
                Bug fixes and pull requests:
                <ul>
                  <li>
                    <div>
                      Trac tickets: <a href="https://svn.boost.org/trac/boost/ticket/13380">#13380</a>, <a href="https://svn.boost.org/trac/boost/ticket/13625">#13625</a>, <a href="https://svn.boost.org/trac/boost/ticket/13637">#13637</a>
                    </div>
                  </li>
                  <li>
                    <div>
                      GitHub Issues: <a href="https://github.com/boostorg/test/issues/149">#149</a>, <a href="https://github.com/boostorg/test/issues/150">#150</a>, <a href="https://github.com/boostorg/test/issues/156">#156</a>, <a href="https://github.com/boostorg/test/issues/158">#158</a>,
                      <a href="https://github.com/boostorg/test/issues/163">#163</a>
                    </div>
                  </li>
                  <li>
                    <div>
                      GitHub Pull Requests: <a href="https://github.com/boostorg/test/pull/147">PR#147</a>, <a href="https://github.com/boostorg/test/pull/148">PR#148</a>, <a href="https://github.com/boostorg/test/pull/151">PR#151</a>,
                      <a href="https://github.com/boostorg/test/pull/154">PR#154</a>, <a href="https://github.com/boostorg/test/pull/161">PR#161</a>
                    </div>
                  </li>
                </ul>
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/type_index/">TypeIndex</a>:</span>
          <ul>
            <li>
              <div>
                Fix the regression and speed up parsing of the <code><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span></code>
                header by 30% (thanks to Nikita Kniazev for the PR!) <a href="https://github.com/boostorg/type_index/issues/21">#21</a>.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/utility/">Utility</a>:</span>
          <ul>
            <li>
              <div>
                Added support for non-inheritable empty types to <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">compressed_pair</span></code>
                by avoiding the empty base optimization for types which are declared
                as final (Glen Fernandes).
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/variant/">Variant</a>:</span>
          <ul>
            <li>
              <div>
                Fixed issue with visibility. Now <code><span class="identifier">boost</span><span class="special">::</span><span class="identifier">bad_visit</span></code>
                exception could cross the boundaries of shared library with hidden
                visibility and could be catched in other shared library with hidden
                visibility.
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          <span class="library"><a href="/libs/yap/">YAP</a>:</span>
          <ul>
            <li>
              <div>
                Minor changes to support MSVC++ version 14.15 (Visual Studio 2017
                version 15.8).
              </div>
            </li>
            <li>
              <div>
                Doc fixes.
              </div>
            </li>
          </ul>
        </div>
      </li>
    </ul>
  </div>
  <div id="version_1_69_0.discontinued_libraries">
    <h3><span class="link">Discontinued Libraries</span></h3>
    <ul>
      <li>
        <div>
          Signals (v1) is now removed. Its removal was announced in 1.68 and its
          deprecation was announced in 1.54. Boost 1.68 is the last release that
          provides this library. Users are encouraged to use Signals2 instead. The
          Boost community thanks Douglas Gregor for his work on Signals which served
          its users well and which also inspired Signals2.
        </div>
      </li>
    </ul>
  </div>
  <div id="version_1_69_0.compilers_tested">
    <h3><span class="link">Compilers Tested</span></h3>
    <p>
      Boost's primary test compilers are:
    </p>
    <ul>
      <li>
        <div>
          Linux:
          <ul>
            <li>
              <div>
                Clang: 3.0, 4.0.1, 6.0.1
              </div>
            </li>
            <li>
              <div>
                Clang, C++0x: 3.0
              </div>
            </li>
            <li>
              <div>
                Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1
              </div>
            </li>
            <li>
              <div>
                Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2,
                6.0.1
              </div>
            </li>
            <li>
              <div>
                Clang, C++17: 5.0.2, 6.0.1
              </div>
            </li>
            <li>
              <div>
                GCC: 4.4.7, 4.5.3, 4.6.3, 5.4.0, 8.0.1
              </div>
            </li>
            <li>
              <div>
                GCC, C++0x: 4.4.7
              </div>
            </li>
            <li>
              <div>
                GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1
              </div>
            </li>
            <li>
              <div>
                GCC, C++14: 5.4.0, 5.5.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1
              </div>
            </li>
            <li>
              <div>
                GCC, C++17: 7.3.0, 8.0.1
              </div>
            </li>
            <li>
              <div>
                Intel, C++14: 18.0
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          OS X:
          <ul>
            <li>
              <div>
                Apple Clang: 9.0.0, 9.1.0, 10.0.0
              </div>
            </li>
            <li>
              <div>
                Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0
              </div>
            </li>
            <li>
              <div>
                Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0
              </div>
            </li>
            <li>
              <div>
                Apple Clang, C++17: 9.1.0, 10.0.0
              </div>
            </li>
            <li>
              <div>
                Apple Clang, C++1z: 9.0.0
              </div>
            </li>
            <li>
              <div>
                Apple Clang, C++2a: 10.0.0
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          Windows:
          <ul>
            <li>
              <div>
                GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4
              </div>
            </li>
            <li>
              <div>
                GCC, C++0x: 4.6.4
              </div>
            </li>
            <li>
              <div>
                GCC, C++11: 4.7.3, 4.8.1, 4.9.3
              </div>
            </li>
            <li>
              <div>
                GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0
              </div>
            </li>
            <li>
              <div>
                GCC, C++17: 7.1.0, 7.2.0, 7.3.0
              </div>
            </li>
            <li>
              <div>
                Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          FreeBSD:
          <ul>
            <li>
              <div>
                Clang: 4.0.0
              </div>
            </li>
            <li>
              <div>
                Clang, C++11: 4.0.0
              </div>
            </li>
            <li>
              <div>
                Clang, C++14: 4.0.0
              </div>
            </li>
            <li>
              <div>
                Clang, C++1z: 4.0.0
              </div>
            </li>
          </ul>
        </div>
      </li>
    </ul>
    <p>
      Boost's additional test compilers include:
    </p>
    <ul>
      <li>
        <div>
          Linux:
          <ul>
            <li>
              <div>
                Clang: 3.0, 3.8.1, 3.9.1, 4.0.1, 5.0.2, 6.0.1
              </div>
            </li>
            <li>
              <div>
                Clang, C++0x: 3.0
              </div>
            </li>
            <li>
              <div>
                Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1
              </div>
            </li>
            <li>
              <div>
                Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2,
                6.0.1, 7.0.0
              </div>
            </li>
            <li>
              <div>
                Clang, C++17: 5.0.2, 6.0.1
              </div>
            </li>
            <li>
              <div>
                GCC: 4.4.7, 4.5.3, 4.6.3, 4.9.4, 5.4.0, 5.5.0, 8.0.1
              </div>
            </li>
            <li>
              <div>
                GCC, C++0x: 4.4.7
              </div>
            </li>
            <li>
              <div>
                GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1
              </div>
            </li>
            <li>
              <div>
                GCC, C++14: 5.4.0, 5.5.0, 6.3.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1, 8.1.0
              </div>
            </li>
            <li>
              <div>
                GCC, C++17: 7.3.0, 8.0.1
              </div>
            </li>
            <li>
              <div>
                Intel, C++14: 18.0
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          OS X:
          <ul>
            <li>
              <div>
                Apple Clang: 9.0.0, 9.1.0, 10.0.0
              </div>
            </li>
            <li>
              <div>
                Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0
              </div>
            </li>
            <li>
              <div>
                Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0
              </div>
            </li>
            <li>
              <div>
                Apple Clang, C++17: 9.1.0, 10.0.0
              </div>
            </li>
            <li>
              <div>
                Apple Clang, C++1z: 9.0.0
              </div>
            </li>
            <li>
              <div>
                Apple Clang, C++2a: 10.0.0
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          Windows:
          <ul>
            <li>
              <div>
                GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4
              </div>
            </li>
            <li>
              <div>
                GCC, C++0x: 4.6.4
              </div>
            </li>
            <li>
              <div>
                GCC, C++11: 4.7.3, 4.8.1, 4.9.3
              </div>
            </li>
            <li>
              <div>
                GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0
              </div>
            </li>
            <li>
              <div>
                GCC, C++17: 7.1.0, 7.2.0, 7.3.0
              </div>
            </li>
            <li>
              <div>
                Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1
              </div>
            </li>
          </ul>
        </div>
      </li>
      <li>
        <div>
          FreeBSD:
          <ul>
            <li>
              <div>
                Clang: 4.0.0
              </div>
            </li>
            <li>
              <div>
                Clang, C++11: 4.0.0
              </div>
            </li>
            <li>
              <div>
                Clang, C++14: 4.0.0
              </div>
            </li>
            <li>
              <div>
                Clang, C++1z: 4.0.0
              </div>
            </li>
          </ul>
        </div>
      </li>
    </ul>
  </div>
  <div id="version_1_69_0.acknowledgements">
    <h3><span class="link">Acknowledgements</span></h3>
    <p>
      Daniel James, Vladimir Prus, Marshall Clow and Michael Caisse managed this
      release.
    </p>
  </div>
</div>
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